Motors that are driven by fluid pressure are not new. Steam engines utilize the expansion of pressurized steam in a cylinder to drive the piston, thereby deriving work energy from the expansion step. Internal combustion engines derive work energy from combustion of fuels in oxygen from the air to drive a piston in a cylinder. In both of these types of motors, the cylinder is subjected to rapid expansion of gasses that push the piston through one step in the power cycle. Depending on the particular type of motor, such as steam, two or four cycle internal combustion or diesel combustion, products are produced that are expelled via exhaust valves and the like.
Hydraulic motors are also used in some instances, where a fluid under pressure is introduced into a cylinder to drive a piston and thus convert hydrostatic energy to movement, usually rotational, by driving a crank shaft and the like. In some cases the hydraulic motor is designed to drive a shaft, usually in combination with a transmission or at gear box.
One form of hydraulic motor that has found use in industry is the low speed/high torque hydraulic motor. These motors have been found to have substantial advantages over systems in which a high speed motor is used in combination with a gear box speed reducer. A significant advantage is that the combination of low speed and high torque provides a large amount of power in a relatively small drive package. Other benefits include low noise and vibration, as well as high energy efficiency. Such low speed and high torque motors are capable of rapid reversal of direction by reversing the direction of hydraulic fluid flow.
These low speed and high torque hydraulic motors come in two basic forms and in a variety of designs. The motors either are gear reduction motors or radial piston motors. In the former, high speed motors are reduced using a complicated series of gears to lower the speed and achieve higher torque. In the latter, various schemes for moving fluids around the axis of a crankshaft have been provided.
Vane motors employ pressure against a plurality of vanes riding on a ring cam to form sealed chambers that carry fluid through the device, optimally at low pressure. The major disadvantage is that there are too many leakage paths. Rolling-vane motors sequence fluid flow to put high pressure against trailing surfaces and low pressure against leading surfaces, but are limited in displacement.
There are also a variety of piston motors. Radial piston motors have a wide displacement range and are very efficient in medium or high displacement ranges. Cam type radial piston motors are less efficient and have difficulty at low speed. Axial piston motors are effective and have good starting torque characteristics. Two sources of heavy duty hydraulic motors are Nutron Motor Co., Inc. in Eliot, Maine, which produces a radial piston hydraulic motor under the MHA series, and Kawasaki Precision Machinery, Inc. which produces radial piston hydraulic motors at its Staffa facility in Plymouth, England.
One of the principle drawbacks to hydraulic motors is that the commercial designs are extremely large for the power that is produced. Both the space or volume taken up by such motors and the weight that is needed are so great as to be seen as drawbacks or handicaps when selection of a motor is being made. In order to have useful torque in industrial applications, such as in heavy equipment, moveable boat and lumber lifts, end loaders, reel drives, winches, and other hub drive designs, great amounts of power is needed. However, all presently known designs are not capable of effectively using the power of a short stroke, high displacement motor arranged within a compact area or motor volume so as to be adapted to the device of interest.
It would be of great advantage if an improved hydraulic motor could be provided that would deliver the same or greater power using less space and having less weight than conventional motors which have been described.
In addition, it would be an advance in the art if high torque, low speed motors could be designed that did not require the use of multiple reducing gears to translate high speed motion into low speed, high torque output.
Further, it would be an advance in the art if a hydraulic motor could be provided that was capable of reversing virtually instantaneously to reverse the movement of any power transmission shaft to which the motor would be attached.
It would be a significant advance if a hydraulic motor could be provided that had the capability of self braking, so that no additional brake device would be needed for the motor, and the equipment to which it is attached, to remain motionless while supporting the full weight of the load being driven. In other words, it would be a great advance if the motor could stop at any pre-selected point and support the load attached thereto without the use of additional brake elements.
Reel handlers for loading and unloading reels from trucks or trailers are not new per se. Some reel handlers allow for powered payout and take-up of cable from the loaded reels by the use of friction rollers contacting the periphery of the reels. Examples are Hall, U.S. Pat. Nos. 3,184,082 and 3,325,118; and Woodruff, U.S. Pat. No. 4,228,967. Skalleberg et al U.S. Pat. No. 5,123,602 discloses a drive for cable reels by the use of frictional contact of the reel periphery with a powered car tire as the roller. However these methods of reel rotation are not precise and braking of the reel by friction contact of the rollers/tires against the reel is less than optimal. Further, powered rotation, and prompt reversal of the rotation, is limited by slippage of the roller at the reel periphery.
It would be an advance in the art if a reel handler could be provided that allowed for precise powered rotation of reels with self-braking features and rapid, almost instantaneous reversal of reel rotation.
McVaugh, U.S. Pat. No. 3,820,673 allows for engagement of reels of varying sizes and permits transfer of one reel to a first location and return for a second reel.
Mechanically complex devices to rotate mounted reels are disclosed in, for example, Berry, III et al., U.S. Pat. Nos. 5,246,180 and 5,333,809. Berry, III et al. require the use of high torque electrical gear motors or motor/gear reducer combinations with drive screw and drive nut arrangements. Similar complex mechanisms are also used in the Berry, III et al. 5,333,809 portal traverse assembly to substantially vary the width between the spaced masts to engage reels of varying sizes. However these motors are complex and relatively heavy. The motors are also large, bulky and require the use of reducing gears to convert the high speed of the motors to the low speed, high torque necessary for controlled reel rotation.
It would be of great advantage if a reel handler could be provided that used motors and devices of few moving parts to engage and rotate reels of varying sizes and to raise and lower the reel to facilitate loading and unloading of the reels from a chassis and payout and take-up of cable from the reel.
Hirakawa et al., U.S. Pat. No. 4,460,135 discloses a mill roll stand that permits raising and lowering of a paper roll and movement of the movable frames holding the paper roll along a threaded shaft. Again this is a mechanism that can be easily damaged.
It would be a advance in the art if a reel handler could be provided that used rugged motors and devices of relatively few moving parts to minimize damage and breakdown of the reel handler during use.
Other devices have been used to load, unload, and in some cases unroll, round hay bales. For example, see Parker, U.S. Pat. No. 3,946,887; and Hostetler, U.S. Pat. No. 4,044,963. Hostetler allows the round bale to be unrolled by controlled positioning of the bale adjacent the ground surface and rolling the bale thereon upon movement of the vehicle. None of the prior art provides for the use of a compact, high torque/low speed motor that is contained within a reel lift arm.
It would be an advance in the art if an improved reel handler could be provided that incorporated a compact, high torque, low speed hydraulic motor within its supporting reel arm to rotate the reel.
The prior art does not provide a safety mechanism that reliably prevents inadvertent release of the engaged reels. Engagement of the reels is of critical importance during transportation of the reels at high speeds along public roads and highways.
It would be a significant advance in the art if a safety device could be provided that reliably prevented inadvertent release of engaged reels.
Accordingly, it is an object of the present invention to provide a hydraulic motor capable of operating under high torque and low speed, such motor being suitable for operation in a smaller space than prior art designs such as within a reel arm of a reel handler.
A further object of this invention is to provide a hydraulic motor capable of producing high torque and low speed without the need for multiple reducing gears to translate high speed motion into the resultant high torque and low speed to make the motor more reliable during use in, for example, a reel handler.
Another object of this invention is to provide a hydraulic motor which is capable of supporting a load at zero velocity without the need or requirement of an additional brake device to facilitate, for example, precise reel payout and take-up of a reel handler.
Yet another object of the present invention is to provide a hydraulic motor capable of almost instantaneous reversal allowing for a like reversal of any power transmission shaft to which the motor would be attached to facilitate, for example, precise reel payout and take-up of a reel handler.
Another object of the present invention is to provide an improved reel handler with relatively few moving parts to engage and rotate reels of varying sizes and to raise and lower the reel to facilitate loading and unloading of the reels from a chassis, and payout and take-up of cable from the reel.
Yet a further object of the present invention is to provide a simple safety device for a reel handler that reliably prevents inadvertent release of engaged reels.
Other objects will appear hereinafter.